In addition to what civac said, if a deal is in danger of being accepted outright, people sometimes add in "war against X" just so you don't accept it.
IE; if I wanted to invite to you war in 10 turns, I'd offer war for war and 10 gold. You might then accept that deal, forcing me into the war right now.
IE; if I wanted to invite to you war in 10 turns, I'd offer war for war and 10 gold. You might then accept that deal, forcing me into the war right now.